Muffles are leather pads fitted to a bell's clapper to reduce the volume. They attenuate the bell's strike note whilst retaining the hum. By only muffling the clapper on one side you get an 'echo' effect as blows are alternately loud and soft. Bells fitted with muffles in this way are said to be half-muffled.
Which Side to Muffle
Bells are usually muffled on the backstroke as the handstroke gap emphasises the echo effect. However, if it is intend to ring the bells down in peal it can be better to muffle the handstrokes. This is because it is the backstrokes that are heard at the end of a fall and they become almost inaudible if the backstoke is muffled. Two muffles can be fitted, one on each side of the clapper, to fully muffle the bell.
Traditionally muffles have leather straps, and these must be buckled very tight to avoid the very annoying sound if one slips round while ringing. Nowadays, velcro is commonly used to provide both a secure fitting and a quick release.
For safety reasons, muffles should always be fitted and removed with the bells down. To muffle the backstroke, put the muffle on the side of the clapper that is furthest away from the pulley. To muffle the handstroke, put the muffle on the side of the clapper that is nearest to the pulley.
Occasions when Bells are rung Half-muffled
Bells are often rung half-muffled at funerals and on Remembrance Sunday as it gives a mournful effect, especially on heavy mellow bells. Some bands also ring this way on New Year's eve to mark the passing of the old year, removing the muffles at midnight to welcome the new year.